The Renewal purchase button is available for an SSL certificate within 30 calendar days before the certificate expires. After the certificate is renewed, the new certificate appears below the original certificate that is about to expire. The 
icon appears to the left of the new certificate, which indicates that the new certificate is associated with the original certificate. The validity period of the original certificate is not changed. The new certificate is in the Pending Application state. You must submit an application for the new certificate, and cooperate with the certificate authority (CA) staff to complete the verification of domain name ownership and the review of application materials. After the CA approves the certificate application, the CA issues the new certificate to you. For more information, see Submit a certificate application.
After the certificate application is approved and the certificate is issued, you can download the certificate based on the type of your server. For more information about how to view the type of a server and download a certificate, see How do I view the type of a server? and Installation overview.